Chapter 15 Puerperium and Lactation AVS 222

1. Chapter 15 Puerperium and LactationAVS 222

2. Puerperium • The period after parturition when reproductive tract repairs itself and returns to its non-pregnant condition (Uterine involution) • Become prepared for another pregnancy • Begins immediately after parturition and recovery period varies among species • Short and smooth recovery period is desirable

4. Events of Puerperium • Myometrium contraction and expulsion of lochia • Endometrial repair • cyclcity: • Elimination of bacterial contamination

6. Stage 1:Myometrium contraction and expulsion of lochia

7. Stage 2 & 3: Endometrial repairResumption of ovarian function • Necrosis of caruncular tissues • Sloughing of the caruncular tissues • Reorganization of uterine endometruim • First postpartum ovulation

8. Stage 4:Elimination of bacterial contamination • Continuation of uterine contraction • Rise in Estradiol and increase in leukocytes • High degree of

11. Lactation

13. The Mammary Gland • Exocrine gland; common to all mammals • Function: nourish the neonate - Food source: fat, protein, sugar (CHO), vitamins, minerals, water - Protection: immunoglobulins

14. The Mammary Gland • Loosely considered part of the reproductive system: • Serves a “reproductive function”; nourishment of the neonate = survival of species. • Relies on same endocrine (hormonal) support for development and function. • Example: gonadal steroids, prolactin, etc.

15. The Mammary Gland Embryo Origin: • The mammary gland is a skin gland – –

16. The Mammary Gland Secretory Tissues: • Glandular; secreting tissue = – Alveoli: – Duct system; lined by epithelial cells – Lobules & lobes; clusters of alveolar tissue supported by connective tissue

19. The Mammary Gland Alveolus: – basic secretory unit; lined by epithelial cells which synthesize and/or secrete: • lipid - triglycerides & free fatty acids (FFA) • protein- • lactose– • minerals & vitamins- Ca, P, K; Vits. A, B, C, D • water

20. Milk Synthesis • Milk synthesis is dependent on: – no. secreting cells – – supply of milk precursor – – milking frequency • No. secreting cells is dependent on: – genetics – endocrine support for mammogenesis – –

21. Blood Components Blood Flow (cattle) Example: What volume of blood would a 1400 lb. Holstein pump per day? 1400 lb. Cow ~ .9 liters/ heart stroke Volume/day = .9 x 70 strokes/min = 63 liters/min 63 liters/min x 1440 min/day = 90,720 liters/day = ~ 22,600 gal/day

22. Blood Components Blood Flow (cattle) • Volume of blood/ volume of milk synthesized = (this is an approximation; actual ratio is affected by stage of lactation, efficiency, etc.)

23. Steroid Hormones and Mammogenesis • Estrogens: • – follicle, placenta, • • Progesterone: • – corpus luteum, placenta, • • Corticoids: • – adrenal cortex

24. Steroid Hormones and Mammogenesis • Estrogens (E2) (follicle, placenta) 1) 2) 3) synergize with progesterone & prolactin to stimulate protein synthesis and duct growth

25. Steroid Hormones and Mammogenesis • Progesterone (P4) (corpus luteum, placenta) 1)stimulates lobulo-alveolar growth– retards milk synthesis 2)retards synthesis of enzymes (a-lactalbumin) necessary for lactogenesis in the prepartum mammary gland

26. Lactogenesis; Cortisol • Action of cortisol:( from adrenal cortex) (dexamethasone is synthetic cort.) 1) synthesis stimulated by maternal, fetal ACTH essential to lactogenesis (adrenalectomy > nolactogenesis) 2)

27. Mammogenesis (Mammary Growth and Development) • Placental E2 + luteal P4 = – duct development – lobulo-alveolar development – suppression of milk synthesis (P4 suppresses -lactalbumin; lactose synthesis

28. Mammogenesis (Mammary Growth and Development) • Action of cortisol + PRL: – increase PRL receptor synthesis – – – increase protein transcription/translation – • cortisol is permissive to action of PRL

29. Lactogenesis (Milk Synthesis) • • How does P4 retard milk synthesis in the nonlactating mammary gland? • Blocks glucocorticoid (cortisol) receptors • • Cortisol + PRL stimulates synthesis of PRL receptors on mammary cells • P4blocks induction of PRL receptors • • Retards synthesis of a-lactalbumin, casein mRNA • • Retards casein, a-alactalbumin, lactose synthesis • thus, retards milk synthesis

30. Endocrine Glands Supporting Mammary Function Posterior pituitary (protein hormones): Oxytocin • Synthesized in the hypothalmus • Ttransferred to post. pit. • Secreted into blood > acts on myoepithelial cells • Contraction of myoepithelial, smooth muscle

32. Endocrine Glands Supporting Mammary Function • • • • increases gluconeogenesis • • increases blood glucose • increases efficiency of • production (greater lbs. of • milk/ lb. DMI) • GH (STH, BST): – increases milk yield Action: • •

33. Endocrine Glands Supporting Mammary Function Pancreas (islets of Langerhans; protein hormones) (responsive to blood glucose concentration) Glucagon (alpha cells): • • increases lipolysis • • increases glycogenolysis • • depresses cellular glucose uptake • • catabolic to adipose, muscle, liver tissue • • increases blood glucose concentration

37. Lactogenesis • Lactogenesis = initiation of milk synthesis – initiated in the E2/P4 “primed” mammary gland when: • corpus luteum regresses • P4 declines • cortisol increases • PRL, GH increase – these circumstances occur at parturition